How to install Meld with Homebrew on Mac OSX?

Homebrew

You can now install Meld with Homebrew! On macOS, run:

$ brew install --cask meld

Other Homebrew Commands

I've changed the syntax of this answer over time to be more fluent. The following commands are equivalent and also work for at least macOS Sierra and High Sierra:

$ brew install --cask homebrew/cask/meld
$ brew install homebrew/cask/meld

You should not run the older $ brew install homebrew/gui/meld because it's deprecated by Homebrew.

As pointed out by @meduz in the comment above, meld now compiles file in brew (haven't tested yet), please try it first, since my original answer is much older.

Today is already possible install it using Homebrew:

brew install meld

I got a issue with pygtk, when I execute meld it says:

Couldn't bind the translation domain. Some translations won't work.
Cannot import: pygtk
No module named pygtk

I already have pygtk installed from lion, and needed to export it to work:

export PYTHONPATH=/usr/local/lib/python2.7/site-packages/

Add the above line to your ~/.profile to set PYTHONPATH automatically when you open a terminal window.

On OSX El Captain you have just to run:

$ brew install homebrew/gui/meld